Apparatus and method for reducing peak-to-average power ratio in a broadband wireless communication system

Abstract

An apparatus and method for PAPR reduction in a wireless communication system are provided. In the PAPR reducing apparatus, a first calculator calculates an ISF for each sample of baseband sample data. A successive peak detector adjusts the ISF of the each sample according to the spacing between successive peak samples. A second calculator subtracts the ISF of each sample received from the successive peak detector from a predetermined value. A window convolution calculator calculates a convolution of the difference received from the second calculator and a predetermined window function, and outputs a window operation value of each sample.

Description

PRIORITY [0001] This application claims priority under 35 U.S.C. § 119 to an application entitled “Apparatus and Method for Reducing Peak-to-Average Power Ratio in a Broadband Wireless Communication System” filed in the Korean Intellectual Property Office on Apr. 20, 2005 and assigned Serial No. 2005-32557, the contents of which are incorporated herein by reference. BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates generally to a Multi-Carrier Modulation (MCM) communication system, and in particular, to an apparatus and method for reducing Peak-to-Average Power Ratio (PAPR) in an Orthogonal Frequency Division Multiplexing (OFDM) system. [0004] 2. Description of the Related Art [0005] OFDM is a special case of MCM, in which a serial symbol sequence is, prior to transmission, converted to parallel symbol sequences and modulated to mutually orthogonal sub-carriers. [0006] The first MCM systems appeared in the late 1950's for military High...

AI Technical Summary

Benefits of technology

[0024] An object of the present invention is to substantially solve at least the above problems and / or disadvantages and to provide at least the advantages below. Accordingly, an object of the present invention is to provide an apparatus and method for reducing PAPR in a multi-carrier communication system.

[0025] Another object of the present invention is to provide an apparatus and method for reducing PAPR by improved peak windowing in a multi-carrier communication system.

[0026] A further object of the present invention is to provide an apparatus and method for preventing excess reduction of the amplitude of an original signal when peaks at or above a threshold appear at smaller intervals than a window size in a multi-carrier communication system for PAPR reduction based on peak windowing.

[0027] Still another object of the present invention is to provide an apparatus and method for reducing PAPR by improved peak windowing so as to decrease average BER, while maintaining spectral characteristics in a multi-carrier communication system.

Problems solved by technology

In view of difficulty in maintaining orthogonal modulation between multiple carriers, OFDM has limitations in applications to real systems.

Despite the above-described benefits, OFDM has the distinctive drawback that MCM causes a high PAPR.

Moreover, if the subcarriers are in phase, this results in a very high amplitude fluctuation.

As a consequence, the signal is out of the linear operation range of a high power amplifier in a Radio Frequency (RF) processor, and after passing through the high power amplifier, signal distortion is produced.

This approach is very simple in terms of system implementation, but despite the use of a filter, hard clipping-caused distortion of frequency spectrum interferes with an adjacent frequency band.

However, when peaks exceeding the threshold successively exist at smaller intervals than the window size W, the amplitude of the original signal is over-limited and thus average Bit Error Rate (BER) is increased during the period of the original signal.

Due to the IFFT process, transmitter complexity increases by almost a factor of M and the transmission of side information is rather constraining.

Since M IFFTs are required and the computation volume of calculating phase factors significantly increases with the number of subblocks, high-speed information transmission cannot be achieved.

Moreover, the scaling factors become negative values, thereby causing problematic errors to the system.

However, this peak windowing technique using feedback still has the problem of excess limitation of the amplitude of the original signal due to the overlapped scaling factors, when peaks are generated at smaller intervals than a window size.

However, if peaks at or above the threshold appear successively, their amplitudes are restricted too much.

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